Absolutely they can, and do. To a point.
But.....
If the season turns and brix can't stay up they are no longer able too.
In the end fungus gets everything. You can't outrun it.It's the floor that everything else lives on when it comes to the food chain.
But in reality, yeah high brix has a great chance because in order to have high brix you need 5 things besides light and minerals. You need calcium, phosphorus, carbon, oxygen, and beneficial microbes.
If you have enough microbes to keep you at high brix they are all over your plant.
They are even inside it in the sap.
Pathogens don't have a chance as the microbes are the immunity, just as the human gut biome is most of our immune system.
So if you can reach harvest with the weather and nutrition to still be high brix you are still healthy, so mildews, etc can't get a hold.
Except, of course, grasshoppers. They are satanic little fucks with no respect for brix.
But if the environment gets too cold and damp for too long you can lose your brix, then you're fair game.
Sugar is a preservative.